storing arithmetic terms to double

i'm a beginner and i'm trying to program a calculator that can handle multiple operations at once. i mean it should be able to calculate what 2/4+86*sin(2*pi) is. the user will enter a term and then an operator and then another term and so on. i'm thinking about storing terms and operators in arrays and then let the computer calculate after the user's done entering new data. so my question is, how am i supposed to store sin(2*pi) in the double array i created to store my terms? is there any way to do this?